1. Field of the Invention
This invention relates to apparatus and methods for testing packaged integrated circuits and, more particularly, to test sockets and methods for failure analysis of quad flat pack QFP integrated circuit devices.
2. Prior Art
Integrated circuits are commonly packaged in a package configuration referred to as a quad flat pack QFP package. In this type of package, the leads are very thin, flat metal conductors which extend outwardly from the four side walls of the flat rectangular package. Inoperative quad flat pack devices are frequently returned by customers to the manufacturer as allegedly defective parts for further testing and failure analysis by the manufacturer. These returned QFP devices are often returned with damaged leads because the customers have performed incoming inspection and in-situ testing of these devices with the devices having been mounted to the actual circuit boards of a system. For customer testing, the individual integrated-circuit devices are soldered to a circuit board and the entire circuit board is tested by the customer. When a particular integrated-circuit device is suspected of being detective, that device is removed from the circuit board by de-soldering. During this de-soldering step, the leads of the device are often severely damaged. This kind of damage to the leads often prevents the integrated-circuit device from being tested on the manufacturer's automatic testing machines to verify that the device itself was defective, rather than damaged or misused by the customer. Customers return defective devices to the manufacturers and request credit, so it is important to the manufacturer that the returned devices be properly retested and analyzed to properly assess the cause of the defect in a device. Because of the damage to the leads on these devices, manufacturers of these returned devices are often unable to perform the necessary failure testing and analysis work to verify the failures as being the responsibility of the manufacturer. In addition, other questions about the devices cannot be investigated and answered, questions such as how, where, and why the device failed. Finally, as a result of the damage to the leads of these devices, the most important aspect of failure analysis cannot be performed, that is, determining the root cause of the failure and requesting corrective action from the responsible areas of the manufacturer or customer.
One technique for testing a damaged quad flat pack QFP leads is to manually solder a test-lead wire to a damaged very thin lead to obtain electrical contact with the pin. This is difficult to do with packages having greater than 100 leads. A historically poor success rate for manually soldering a test-lead wire to damaged leads indicates that a better, more efficient technique is needed for retesting returned damaged QFP devices on a manufacturer's automatic testing machines.
Consequently, the need exists for a technique for testing and performing failure analysis of damaged QFP integrated-devices which have been returned by customers to manufacturers as defective parts. Such a technique would significantly reduce the manufacturer's liability for the mistakes of their customers in handling, testing, and/or using QFP integrated-circuit devices.